1. Field of the Invention
The present invention is directed to protein patterning through application of an electric charge to a surface having no or minimal attraction for proteins, and to a method of protein patterning using such devices.
2. Background Art
Patterning of proteins is a useful technique with numerous applications, including biological sensors, bioanalyses, and as protein concentrators prior to analysis by other methods. Proteins can be patterned on surfaces to which they are adherent, and such methods have been widely used. One example is the deposition of bovine serum albumin (BSA) onto glass or silicone elastomer surfaces. By coating portions of these surfaces with coatings to which proteins do not adhere, protein patterns may be generated. However, the patterns thus produced are relatively permanent, i.e. not easily reversible.
Very few if any electrical methods exist for immobilizing proteins on a surface. Most of the existing methods are based on irreversible biochemical processes or surface chemistry occurring on photolithographically defined surface patterns. They require a new surface with all new photolithographic masks when a new pattern of proteins is desired. In that sense, the conventional approaches are “static” without providing a surface with the capability of patterning proteins in a reconfigurable manner. In other words, once a desired arrangement or protein is figured into the device design, it can not be changed.
Thermal methods that change a surface from a hydrophobic to a hydrophilic state have been used for protein patterning. In such methods, variation of temperature causes a change in the surface affinity of proteins. Proteins bound to a surface at elevated temperatures are released when the surface temperature is returned to room temperature. Such thermal methods are not useful when the orientation of the bound protein is important. Moreover, these methods cannot control the amount of adsorbed protein as the entire surface becomes hydrophilic and so the proteins bind with a weak ionic bond. Accordingly, the amount of bound protein can not be controlled using this method in that proteins either bind and cover the surface entirely or do not. Precise control of the temperature is necessary to ensure that denaturing of the proteins does not occur. Since the thermal method involves only a weak bond, its protein binding mechanism is highly susceptible to molecular diffusion processes. It follows that surface-bound proteins could be quickly replaced with proteins of higher molecular weight. In contrast, our method ensures that proteins remain in place without being affected by introducing other proteins. Once they are bound under an applied voltage a strong ionic bond is formed and the proteins can be released when the voltage is turned off through diffusion.
Accordingly, it is desirable to develop new methods and devices for preparing protein patterns, particularly protein patterns which are susceptible to ready protein removal, and in particular to provide devices which are reconfigurable to protein patterning.